Photographic apparatus with dynamically controlled reflex action

ABSTRACT

Reflex photographic apparatus incorporating an reflecting member which is moved during a photographic cycle to convert an optical path from viewing-focusing to exposure configurations. A low-rate torsion drive spring moves the reflecting member from a viewing position to an exposure position quickly, while minimizing elastic rebound at the termination of movement. A motor is used to return the reflecting member to its viewing position following a photographic exposure. Mounted coaxially with, and disposed within the drive spring, is a second low-rate torsion spring which is operative to provide a lost-motion connection between the reflecting member and the return motor. Should the reflecting member be restrained during its return movement, the lost-motion connection permits the motor to complete its cycle without overloading.

United States Patent V [151 3,685,416 i 1 Aug. 22, 1972 CoughlanPHOTOGRAPHIC APPARATUS WITH DYNAMICALLY CONTROLLED REFLEX ACTION [72]Inventor: Edward H. Coughlan, Canton,

Mass.

[73] Assignee: Polaroid Corporation, Cambridge,

Mass.

[22] Filed: Dec. 31, 1970 [21] Appl. No.: 103,219

[52] US. Cl ..95/42, 95/13 [51] Int. Cl. ..G03b 19/12 [58] Field ofSearch ..95/42, 13

[56] References Cited UNITED STATES PATENTS 2,997,934 8/1961 Heerklotz..95/42 3/1964 Wiessner et al. ..95/42 Primary Examiner-Samuel S.Matthews Assistant Examiner-E. M. Bero Attorney-Brown and Mikulka,Gerald L. Smith and William D. Roberson [57] ABSTRACT Reflexphotographic apparatus incorporating an reflecting member which is movedduring a photo graphic cycle to convert an optical path fromviewingfocusing to exposure configurations. A low-rate torsion drivespring moves the reflecting member from a viewing position to anexposure position quickly, while minimizing elastic rebound at thetermination of movement. A motor is used to return the reflecting memberto its viewing position following a photographic exposure. Mountedcoaxially with, and disposed within the drive spring, is a secondlow-rate torsion spring which is operative to provide a lost-motionconnection between the reflecting member and the return motor. Shouldthe reflecting member be restrained during its return movement, thelost-motion connection permits the motor to complete its cycle withoutoverloading.

11 Claims, 5 Drawing Figures PATENTED M1922 I973 3 6 85 4 l 6 smzn 1 BF3 0 9 cu E-L (\l INVENTOR. EDWARD H. COUGHLAN BY J A TTORNEYSPHOTOGRAPHIC APPARATUS WITH DYNAMICALLY CONTROLLED REFLEX ACTIONBACKGROUND OF THE INVENTION The operation of single-lens reflex camerasgenerally includes the steps of viewing and focusing the image of asubject through the cameras objective lens and actuating a shutterrelease button. This actuation closes the camera shutter, moves thecameras reflecting member to an exposure position which allows exposureof a film unit, operates the shutter to make the expo sure, and returnsthe reflecting member to its initial pre-exposure or viewing position inpreparation for a next exposure cycle. Movement of the reflecting memberbetween its viewing and exposure positions generally is carried out bydrive spring arrangements. Inasmuch as it is desirable to complete aphotographic cycle in a minimum amount of time, particularly withhand-held reflex cameras, reflex conversion by the cameras reflectingmember should be carried out in a minimum amount of time. Theminimization of the time required for this activity can be achieved bydriving the reflecting member with relatively powerful springs. Althoughsuch springs move the reflecting member to its exposure position in aminimum amount of time, they introduce problems of halting it at itsterminal operating position. For instance, in the absence of complexdamping, the reflecting member may bounce when it reaches its exposureposition. Such dynamic instability at the exposure position oftenproduces unacceptable camera vibrations. The elimination of suchvibration becomes most important, however, when the reflecting memberforms part of a taking optical path. With such reflex systems, and unduedynamic instability of the reflecting member at its exposure positionproduces focusing error.

Fully automated cameras usually incorporate an electronic motor as apower source for carrying out film processing operations following theexposure of a film unit. Where the automated cameras utilize a reflexviewing system, their reflex mode converting reflecting memberspreferably are cocked following an exposure using power derived from themotor. As a consequence, the reflecting member drive system will usuallyrequire an overtravel form of drive linkage to assure proper seating atits cocked position. These overtravel features are difficult toincorporate within the confined housings of compact cameras withoutresorting to the use of relatively high-torque rate springs. The loadsimposed therefrom upon a small drive motor are difficult to accommodate.

If the reflecting member encounters any interference during its movementtoward its cocked or preexposure position, the motor may be overloadedand damaged. If the motor is overloaded enough, the power drain upon apower supply, such as a battery, may render it incapable of carrying outother powered functions during a given photographic cycle.

SUMMARY OF THE INVENTION The present invention is addressed to camerasof the single-lens reflex type and, more specifically, to a drive systemincluding a lost-motion connection for moving an reflecting memberbetween a viewing position and an exposure or erected position. Movementof the reflecting member between these positions is accomplished througha system incorporating a four-bar linkage and a drive spring. The systemis configured to minimize the time required for moving the reflectingmember to its exposure position. Additionally, the system is configuredto minimize the elastic rebound of the reflecting member which isgenerated as a result of driving the member to its exposure position ata relatively fast rate.

In a preferred embodiment of the invention, a lowrate torsional drivespring is employed for moving the reflecting member to its erectedposition. Such springs are characterized in providing a low-torquedissipation through their excursion angle. When properly prewound, thelow-rate drive spring not only minimizes the reflecting member movementtime but also reduces its elastic rebound amplitude when suddenly haltedat an exposure position. This is achieved by maximizing the residualtorque of the drive spring at the erected position of the reflectingmember. As another feature, an erecting linkage is positioned betweenthe reflecting member and the drive spring to minimize any warping ofthe reflecting member due to a direct coupling thereof with a drivespring.

A prewound overtravel torsion spring is provided within the drive systemand is configured to serve a dual purpose. The overtravel springfunctions to ensure that the reflecting member is fully seated in itsviewing position by allowing a motor to remain energized for a selectinterval following the seating of the member. The overtravel springabsorbs the resultant overtravel motion and biases the member into itsviewing position. This permits more easily met manufacturing tolerancesin the reflecting member-return mechanism since the components thereofdo not have to cooperate to move the reflecting member the precisedistance between its exposure position and viewing position.Additionally, the overtravel spring serves to provide an override orlost-motion connection between the motor and the reflecting member. Ifthe reflecting member encounters any interference during its motordriven movement between exposure and viewing positions, the overtravelspring will allow the motor to finish its normal return cycle. Theenergy from the motor will be transferred to, and stored in, theovertravel spring until such time as the interference is removed. Atsuch time, the overtravel spring returns the reflecting member to itsview ing position. In this manner, any overload or damage to the motorwill be alleviated.

Another object and feature of the invention is to provide a reflexphotographic apparatus having an reflecting member movable between aviewing position and an-exposure position, an erecting linkage formoving the member between its positions, a motor for supplying power tomove the reflecting member from its exposure position to its viewingposition, a drive spring for actuating the erecting linkage, and anovertravel spring coupled between the linkage and the motor foractuating the linkage to drive the reflecting member to one of itspositions and for providing a lost-motion connection with the motor whenthe reflecting member is restrained.

Another object and feature of the present invention is to provide aphotographic apparatus of the reflex type including a low-rate drivespring for moving an reflecting member from its viewing position to itsexposure position in a minimum amount of time, but which will reduce theelastic rebound of the reflecting member when it is suddenly halted atits exposure position.

Another object and feature of the present invention is to provide areflex photographic apparatus including an reflecting member movablebetween viewing and exposure positions, a low-rate drive spring formoving the reflecting member from its viewing to its exposure position,motorized drive means for moving the reflecting member from its exposureto its viewing position, and a low-rate overtravel spring for enablingthe motorized drive means to overtravel beyond a point necessary to movethe reflecting member into its viewing position, thereby seating thereflecting member without having to depend upon close manufacturingtolerances within the motorized drive means.

Other objects and features of the invention will in part be obvious andwill in part appear hereinafter.

The invention accordingly comprises the apparatus possessing features,techniques, and properties which are exemplified in the description tofollow hereinafter.

For a fuller understanding of the nature and objects of the invention,reference should be made to the following detailed description taken inconnection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevated view, partly insection, of a collapsible type, single-lens reflex camera, the camerabeing shown in its extended or operative position;

FIG. 2 is an enlarged fragmentary view of the rear of the camera withportions broken away to reveal internal structure;

FIG. 3 is a sectional view of the apparatus taken through the plane ofline 3-3 in FIG. 2;

FIG. 4 is an enlarged perspective view of a portion of the apparatus asshown in FIG. 1; and

FIG. 5 is a graph of the spring rates of two springs incorporated in theapparatus.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to FIG. 1 of thedrawings, there is shown a camera of the extensible type, the camerabeing shown in its extended or operative position. Camera 10 includes aplurality of housing sections 12, 14, 16 and 18 suitably pivoted to eachother about axes 20, 22, 24 and 26 for movement between the extendedposition shown and a compact folded position wherein housing sections 14and 16 cooperate to define the top wall (as viewed in FIG. 1) of thecamera and surface 28 of housing section 18 cooperates with an endportion of housing section 12 to define an end wall of the camera.Housing sections 12, 14, 16 and 18 cooperate with each other, in theextended position, to define four sides of a six-sided exposure chamber30, the remaining two sides of the chamber 30 being closed by a flexiblebellows 32 formed of any suitable opaque plastic material. Bellows 32includes a plurality of creases 34 which constitute a memory system forensuring that the bellows 32 collapses in a predetermined manner whenthe camera is folded.

Housing section 12 includes means (not shown) for mounting a pair ofmotor driven processing rolls 36 and a film container 38 such that theforwardmost film unit 40 located within the container 38 is located inposition for exposure by light transmitted through an exposure aperture42 located in wall 44 of the container 38.

For a more detailed description of such a camera 10, reference should bemade to a photographic apparatus described and claimed in a copendingapplication for US. Pat. by Edwin H. Land entitled Reflex Camera," filedApr. 4, I970, Ser. No. 28,567, and assigned in common herewith.

Film units 40 (only two of which are shown) are similar to those shownin U.S. Pat. No. 3,415,644 and generally include a photosensitiveelement 46, a superposed transparent image-receiving element 48 and apod 50 containing a processing liquid attached near one end of the twoelements. After exposure, the forwardmost film unit is advanced by anysuitable means from the container into the bite of motor drivenprocessing rolls 36 wherein the pod 50 is ruptured and the liquidcontained therein is evenly distributed between the photosensitive andimage-receiving elements to initiate a diffusion transfer process as ismore fully described in the aforementioned patent.

The cameras optical system generally includes a lens and shutterassembly 52, a generally planar reflecting surface, e. g., a mirror 54mounted on an interior wall of housing section 14, an reflecting member56 and a rangefinder and/or viewfinder (not shown). Reflecting member 56includes a mirror mount 58 which carries a Fresnel-type mirror 60 on oneside thereof and a generally planar mirror 62 on the opposite sidethereof. As can be seen in FIG. 1, member 56 is pivotally mounted to thecamera about pin 82 for movement between an exposure position shown insolid lines and a viewing position as shown in broken lines in FIG. 1.

During operation of camera 10, the reflecting member 56 is initially inthe broken line position shown in FIG. 1. The image of the subject to bephotographed is transmitted by the cameras objective lens 52 into theinterior of exposure chamber 30 wherein it is reflected by mirror 54onto Fresnel-type mirror 60 and thence to the cameras viewfinder. Afterthe image has been properly focused, the cameras shutter actuatingbutton is depressed to close the shutter and the viewfinder aperture andstop the entry of all actinic light into chamber 30. Next, thereflecting member 56 is driven from the viewing position to the exposureposition shown in solid lines in FIG. 1 by a drive spring. When member56 reaches its exposure position, the shutter is operated to make theexposure, and the image is directed toward the film unit 40 by mirror62.

Referring additionally to FIGS. 2 and 3, the motorized drive componentspositioned along the rearward edge of housing section 12 are revealed indetail along with the spring-driven mounting of reflecting member 56. Anelectric motor 66 is attached to the rear portion of housing 12 and isoperative to supply power to a force-transmitting assembly of suitableconstruction shown generally at 68 as well as to processing rolls 36. Anoutput shaft 70 of motor 66-is connected to an input gear 72 of assembly68 through a spring-type slip clutch 74. Spring 74 is frictionallyattached between output shaft 70 and a drive shaft 76, connected to gear72. Shaft 76 is fixed to gear 72 and is rotatably supported within abushing 78 formed as a portion of housing section 12 of camera 10. Awasher 80 is connected to shaft 76 for retaining it within bushing 78.Spring 74 is configured to release from its frictional engagementbetween shafts 70 and 76 should the load imposed upon motor 66 exceed apredetermined limit.

Reflecting member 56 is driven between its operational positions by afour-bar linkage assembly. The components of this four-bar linkageinclude the pivotal coupling at shaft 82 of a hinge extension 84 ofoperator assembly 56. Hinge extension 84 is configured to retain anothershaft 86 spaced forwardly from shaft 82. Hinge extension 84 isadditionally configured having an access slot 88 within which pivotalconnection between shaft 86 and a draw-down link 90 is effected.Drawdown link 90 is pivotally connected through a shaft 92 to the tip ofdual arm portions 94 of a bell crank shown generally at 96. Forming thefinal component of the four-bar linkage, the hub portion 98 of bellcrank 96 is rotationally mounted upon the necked-down or stepped-downportion 100 of a cylindrical shaft 102. Portion 100 of shaft 102 isrotatably supported within a bushing 104 which is fixed to an extension106 of housing section 12. A washer assembly 108 is connected to the endof portion 100 and serves to limit the longitudinal movement of shaft102. The opposite end of shaft 102 is rotatably supported within abushing 1 formed within portion 112 of housing section 12.

Reflecting member 56 is retained in its viewing mode orientation byvirtue of the outward orientation of the dual arms 94 of hell crank 96.Reflecting member 56 is driven to its exposure mode orientation, shownpartially in phantom at 56, by a driving force exerted from bell crank96 through draw-down link 90. The exposure mode orientations of bellcrank 96 and draw-down link 90 are shown in phantom at 96 and 90',respectively. Reflecting member 56 is driven into its exposure positionas well as returned to its viewing position by forces exerted from hellcrank 96 through draw-down' link 90.

A low-rate multi-turn torsion spring 114 is used for powering bell crank96 to drive reflecting member 56 into its exposure position. One end 116of spring 114 is fixed or grounded to frame portion 112, while itsopposite end 118 is configured to abut against the tang portion 120 of acylindrically-shaped sleeve 122.

Referring additionally to FIG. 4, sleeve 122 generally is configured asa hollow right cylinder having a thickened end portion 124 (FIG. 2), theinternal surface of which is bored to fit over a stepped-up portion 126of shaft 102. Sleeve 122 is fixed to and co-rotatable with shaft 102 asa result of its connection thereto by a pin 128. Beyond thickenedportion 126, sleeve 122 slidably couples over hub 98 of bell crank 96.This same end portion of sleeve 122 is cut away to provide top andbottom abutting key surfaces at 130 and 132. In operation, surfaces 130and 132 of sleeve 122 selectively abut against dual arm portion 94 ofbell crank 96. When spring 114 is loaded or wound, its movable end 118abuts against tang 120 of sleeve 122, urging it to rotate in acounterclockwise direction as viewed in FIG. 3. Surface 132 of sleeve122 abuts against arm portion 94- of bell crank 96, biasing the latterto move correspondingly. As a result, when shaft 102 is free to rotate,spring 114 will rotate sleeve 122 in a counterclockwise direction (FIG.3). Due to the abutting engagement between arm portions 94 and bottomkey surface 132, sleeve 122 will drive bell crank 96 to its position asshown at 96. This rotation of bell crank 96 causes draw-down linkage tomove to its position at 90' as shown in FIG. 3. The upward movement ofdrawdown link 90 rotates hinge extension 84 in a clockwise directionabout shaft 82 causing reflecting member 56 to move to its erectedexposure position.

Mounted coaxially with spring 114 over the central portion of shaft 102is an overtravel torsion spring 134. Spring 134 is located within theinterior of sleeve 122. One end 136 of spring 134 is connected withinthe thickened portion 124 of sleeve 122. The opposite end 138 of spring134 is connected to bell crank 96 by insertion within a slot 140 formedin hub 98. Spring 134 is selectively prewound and has a strengthsufficient to urge bell crank 96 toward key surface 132 of sleeve 122.

Following an exposure interval, motor 66 is energized to power rolls 36and cock reflecting member 56. The latter operation is carried out byrotatably driving shaft 102 through its connection with a drive bellcrank 142 mounted at the outward end of shaft 102. Bell crank 142 isfixed to stepped-up portion 126 of shaft 102 by a pin 144 extendingtherethrough and includes an upwardly extending arm portion 146. The tipportion of arm 146 is configured having a hole 148 to provide a pivotalconnection with a pin 150 integrally formed with a reduction assemblyoutput link 152.

With the arrangement thus described, when shaft 102 is rotated during acocking operation, rotational force will be transmitted through bothovertravel spring 134 and sleeve 122 into hell crank 96. Rotation ofsleeve 122 from shaft 102 also winds spring 114 from tang 120. As theunited sleeve 122 and bell crank 96 are rotated, reflecting member 56 isrepositioned by the four-bar linkage into its viewing position adjacentthe exposure plane as shown in phantom in FIG. 1.

Overtravel spring 134 provides a lost-motion or override functionpermitting motor 66 to operate for a select interval of time followingthe seating of reflecting member 56 into its viewing mode position. Thisallows for greater latitude in manufacturing tolerances of the drivesystem since the various components of the system do not have tocooperate to move reflecting member 56 a precise distance; i.e., theexact distance between the exposure and viewing positions. Additionally,spring 134 provides a lost-motion connection between motor 66 andreflecting member 56 should the reflecting member 56 be jammed orinterfered with during conversion from its exposure to its viewing mode.In the latter regard, it may be noted that the cutaway portion of sleeve122 does not fully capture the extensions 94 of bell crank 96. As seenin FIG. 3, a spacing allowing about 45 of relative rotation is pro videdbetween surface 130 of sleeve 122 and arm portion 94 of bell crank 96.

OPERATION A photographic cycle is commenced by depression of a shutterrelease button (not shown) mounted upon camera 10. Output link 152 isreleased for free travel at and movement by a central mechanism (notshown). As a result, bell crank 142 and shaft 102 become freelyrotatable and drive spring 114 rotates sleeve 122 in a counterclockwisedirection (FIG. 3). Since arm portions 94 of bell crank 96 are inabutting engagement with bottom key surface 132, the sleeve 122 drivesbell crank 96 to its position at 96'. This rotation of bell crank 96causes draw-down link 90 to move upward to its position at 90'. Theupward movement of drawdown link 90 rotates hinge extension 84 in aclockwise direction about shaft 82 causing reflecting member 56 to moveto its erected exposure position as shown at 56'.

It is operationally desirable to configure drive spring 1 14 in such amanner as to move reflecting member 56 to its exposure position in aminimum amount of time. This may be accomplished by making spring 114larger. However, with the introduction of a larger drive spring, thereis encountered a problem of elastic rebound when reflecting member 56reaches its exposure position. This undesirable rebound is a result ofdriving reflecting member 56 upward and then immediately halting it.Since planar mirror 62 is formed as a part of reflecting member 56 andis positioned within the taking optical path, any dynamic instability ofthe member may cause focusing error. To minimize this error, drivespring 114 is configured as a low-rate torsion spring. Low-rate springsare characterized in providing a low torque dissipation through a givenexcursion angle. Accordingly, low-rate drive spring 114 is operative tomove reflecting member 56 from its viewing to its exposure positionwhile retaining a select amount of residual torque at the exposureposition. This residual torque serves not only to retain the member 56in position but also to damp or overcome any tendency it may' have tobounce.

After an exposure is completed, electrical switches within camera areclosed to energize motor 66. Motor 66 commences to rotate shaft 70. Thisrotation is translated through force-transmitting assembly 68 to outputlink 152 and thence through arm 146 to shaft 102. Shaft 102 is caused torotate in a clockwise direction, as seen in FIG. 3, and, due to theconnection between shaft 102 and sleeve 122, the latter is movedcorrespondingly. Overtravel spring 134 transmits rotational movementfrom sleeve 122 to bell crank 96. Bell crank 96 and draw-down link 90are moved from positions at 96' and 90' to positions at 96 and 90,respectively, as shown in FIG. 3. As a result, reflecting member 56 ismoved from its exposure to its viewing position.

Overtravel spring 134 is operative to properly seat reflecting member 56in its viewing position. During this operation, motor 66 operates for aselect interval of time following the movement of reflecting member 56into its viewing position. At that time, bell crank 96 ceases to rotateand overtravel spring 134 is operative to absorb the overtravel rotationof sleeve 122. During such overtravel, bottom key surface 132 is movedout of its abutting engagement with arm portions 94 of bell crank 96.The rotation of sleeve 122 and tang 120 causes drive spring 114 to bewound in preparation for a next succeeding photographic cycle. Thisovertravel tensioning, in addition to the prewinding of spring 134,provides a latching bias to bell crank 96, retaining reflecting member56 in its viewing position. As a result, the need for closemanufacturing tolerances within the motor drive linkage for movingreflecting member 56 from its exposure to its viewing position isalleviated.

Overtravel spring 134 is operative as a lost-motion connection betweenmotor 66 and reflecting member 56. If reflecting member 56 encountersany significant interference during movement between its exposure andviewing positions, e. g., some object is inadvertently positioned in itspath of travel, the lost-motion connection of overtravel spring 134operates to prevent damage to the erecting components of the camera.Spring 134 will allow motor 66 to continue to rotate sleeve 122 untilmotor 66 has reached the end of its cocking cycle without transmittingthis rotational force to reflecting member 56.

The lost-motion connection provided by spring 134 functions as follows.At the commencement of a cocking operation, reflecting member 56 is inits expoarm 146. Arm 146 is rotated toward the rear of camera 10, movingshaft 102 and sleeve 122 correspondingly. If during the movement of arm146 the reflecting member 56 is stopped in its downward movement, hingeextension 84 and bell crank 96 will also stop. However, arm 146continues to rotate sleeve 122 from shaft 102. As sleeve 122 continuesto rotate, the abutting engagement between arm portions 94 of bell crank96 and bottom key surface 132 is broken. Sleeve 122 will continue torotate until top key surface approaches a position of abutment with armportions 94. In the embodiment illustrated, a 45 override rotation isallowed. This rotation is sufficient to permit motor 66 to finish itscocking cycle and turn off. When the source of interference has beenremoved, spring 134 releases the energy previously stored therein anddrives bell crank 96 in a clockwise direction until reflecting member56vis seated in its viewing position.

Preferably, overtravel spring 134 is preloaded to provide a residualdownward bias to bell crank 96 for properly retaining reflecting member56 at its viewing position. Additionally, spring 134 is configuredhaving as low a rate as possibledue to-its driven relationship withmotor 66 during override operation. Motor 66 must provide power totension spring 134 a sufficient amount so that when motor 66 completesits cycle, spring 134 will drive bell crank 56 downward into its viewingposition. In addition to winding overtravel spring 134 during anoverride operation, motor 66 must also provide power to wind drivespring 114 to its prewound condition. Accordingly, the energy whichmotor 66 must expend during override operation should not substantiallyexceed that amount expended during normal operation or the motor will beoverloaded.

FIG. 5 shows the spring rates of drive spring 114 and overtravel spring134. Both drive spring 114 and overtravel spring 134 are prewound aselect amount. In the present embodiment, reflecting member 56 traversesan angle of about 37 during its movement from its viewing position (0)to its erected exposure position (37).

During normal operation, drive spring 114 is operative to movereflecting member 56 from 0 to 37, ex-

pending torque at a rate shown by line 154. Overtravel spring 134, dueto the lack of relative movement between bell crank 96 and sleeve 122during this operation, will not expend any torque as shown by line 156.At the exposure position (37), drive spring 114 retains a loaded statusas shown by point 158. The amount of torque which is retained by drivespring 114 at its terminal position of 37 is determined by the amount ofits prewinding. It is this amount of torque which provides residualforce for minimizing the elastic rebound of reflecting member 56 at itsexposure position. After an exposure has been completed, motor 66operates to rewind drive spring 114 an amount y" to its cocked or loadedorientation. Overtravel spring 134 retains its prewound condition and nofurther tensioning from motor 66 is required. Spring 134 has beenprewound an amount x" for properly seating reflect ing member 56 at itsviewing position For purposes of simplifying the description of overrideoperation, interference of reflecting member 56 is assumed to occur at37. Motor 66 rewinds drive spring 114 the same amount y" as it didduring normal operation. However, overtravel spring 134 is wound anamount 2. This additional amount of torque is sufficient to drive bellcrank 96 to its viewing mode orientation when the interference ofreflecting member 56 has been removed. Upon removal of the interference,overtravel spring 134 releases this torque 2 into bell crank 96 andreturns to its prewound status (0).

The total tensioning (y and z") of springs 114 and 134 should beminimized in order to keep motor 66 from overloading. This isaccomplished by making the spring rates of springs 114 and 134 as low aspossible; i.e., configuring both of them as multi-turn torsion springs.However, due to the thin and compact nature of camera 10, suchmulti-turn springs are not easily positioned within the internalstructure of camera 10. In order to position two multi-turn springs in alimited area, overtravel spring 134 is placed within drive spring 1 14.

The coaxial positioning of springs 114 and 134 provides an additionaladvantage. Due to the positioning of drive spring 114 away fromreflecting member 56, any possible warp to be realized from the directlinkage of a drive spring with an optical surface as at 62 will beminimized.

Since changes may be made in the above apparatus without departing fromthe scope of the invention herein involved, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. Reflex photographic apparatus comprising:

means defining an optical path having one configuration for viewing theimage of a scene to be photographed, and another configuration forimaging said scene at an exposure plane;

reflecting means movable between a viewing position and an exposureposition for selectively converting said optical path from one saidconfiguration to the other;

a motor;

erecting linkage means coupled with said reflecting means and actuableto move said reflecting means between said viewing and said exposureposition;

spring loaded drive means engageable with said erecting linkage meansfor actuating said erecting linkage means to move said reflecting meansfrom said viewing position to said exposure position; and

Overtravel spring means coupled with said erecting linkage means anddrivable from said motor to actuate said erecting linkage means to movesaid reflecting means into said exposure position, said overtravelspring means being operative as a lostmotion connection with said motorwhen said reflecting means is restrained from movement.

2. Reflex photographic apparatus comprising:

means defining an optical path having one configuration for viewing theimage of a scene to be photographed and another configuration forimaging said scene at an exposure plane;

reflecting means movable between a viewing position and an exposureposition for selectively converting said optical path from one saidconfiguration to the other; erecting linkage means coupled with saidreflecting means and actuable to move said reflecting means between saidviewing and said exposure positions;

drive spring means for providing a rotational output of predeterminedcharacteristic;

actuator means drivably engageable with said linkage means andresponsive to said drive spring means output for actuating said erectinglinkage means to move said reflecting means from a select one of saidpositions to the other;

motor means having an output connected in driving relationship with saidactuator means for causing said actuating means to actuate said erectinglinkage means to move said reflecting means into said one of saidpositions; and

overtravel means coupled between said actuator means and said erectinglinkage means and operative as a lost-motion connection with said motormeans when said reflecting means is restrained.

3. The reflex photographic apparatus of claim 2 in which said drivespring means is a low-rate multi-turn torsion drive spring having apredetermined residual torque when said reflecting means is in saidother position.

4. The reflex photographic apparatus of claim 2 in which said overtravelmeans is a low-rate multi-turn torsion spring positioned concentricallywith said drive spring means.

5. The reflex photographic apparatus of claim 2 in which:

said drive spring means is a multi-turn torsion drive spring having apredetermined residual torque when said reflecting means is in saidother position;

said actuator means includes sleeve means for drivably engaging saiderecting linkage means; and said overtravel means is positionedcoaxially with said sleeve means and said drive spring.

6. The reflex photographic apparatus of claim 5 in which said overtravelmeans is operative to effect said engagement between said sleeve meansand said erecting linkage means.

7. The reflex photographic apparatus of claim 6 in which said overtravelmeans is present as a multi-turn torsion spring.

which said sleeve means is configured to rotate out of said engagementwith said erecting linkage means when said reflecting means isrestrained and said motor means is energized.

11. The reflex photographic apparatus of claim 6 in which said erectinglinkage means is present as a fourbar linkage.

Patent No.

Dated August 22, 1972 Column change Column change Column change Columnchange Column change Column change Column delete Column Attest f EDWARDI I.FLETSETER,JR. Attesting Officer FORM PO-IOSO (IO-69) 1, lineInvenwfl Edward H. Coughlin I It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

35 (Specification page 1, line 30) "and" to ---any--.

1, line II arl II 2, line ll a II to 2, line II an" 3,, line "an" to 4}line n" 9, line 66 (Specification page 2, line 28) 52 (Specificationpage 4, line 19) 67 (Specification page 5, line 3) 7 (Specification page5, line 9) 27 (Specification page 8, line 4) l6 (Specification page l8,line 5) and insert --Overtravel spring-- 10, line 6 (Claim 1, line 19)(Amendment claim 1, change "Overtravel" to -overtravel--.

line 20) Signed and sealed this lL th day of May 197L G. MARSFALL DANNCommissioner of Patents USCOMM-DC 60376-969 i 0.5. covumnnlv IIIIIT'NGonlcl nu o-Ju-Ju UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 3,685,416 Dated August 22, 1972 Inventofls) Edwa cl H.Coughlin It is certified that eror appears in the above-identifiedpatent: and that said Letters Patent are hereby corrected as shownbelow:

Column 1, line 35 (Specification page 1, line 30) change "and" to--any--.

Column 1 line 66 (Specification page 2, line 28) change "an" to --a--. Iv Column 2, line 52 (Specification page 4, line 19)" change "an" to--a--. Column 2 line 67 (Specification page 5, line 3) change 'an'l to-a--. I Column 3,1 line 7 (Specification page 5, line 9) change "an" to-a--. Y

Column 4} line 27 (Specification page 8, line 4) change "an" to --a-:-.I a 7 Column 9, line 16' (Specification page 18, line 5) delete "Spring"and insert -'-0vertravel spring- Column 10, line 6 (Claim 1, line 19)(Amendment claim 1, line 20) I change "Overtravel'V' to --overtravel-.

' Signed and sealed this lhth day of May 197L M II(. SEAL) I. Attest: gY

EDWARD M.FLETGHEE,JR; Q C. MARSHALL DANN Attesting Officer ICommissioner of Patents FORM 90-1050 (O-69) USCOMM-DC GONG-P69 i 0.5.eovnmmn nmmnc ovncc nu o-uc-a q

1. Reflex photographic apparatus comprising: means defining an opticalpath having one configuration for viewing the image of a scene to bephotographed, and another configuration for imaging said scene at anexposure plane; reflecting means movable between a viewing position andan exposure position for selectively converting said optical path fromone said configuration to the other; a motor; erecting linkage meanscoupled with said reflecting means and actuable to move said reflectingmeans between said viewing and said exposure position; spring loadeddrive means engageable with said erecting linkage means for actuatingsaid erecting linkage means to move said reflecting means from saidviewing position to said exposure position; and Overtravel spring meanscoupled with said erecting linkage means and drivable from said motor toactuate said erecting linkage means to move said reflecting means intosaid exposure position, said overtravel spring means being operative asa lost-motion connection with said motor when said reflecting means isrestrained from movement.
 2. Reflex photographic apparatus comprising:means defining an optical path having one configuration for viEwing theimage of a scene to be photographed and another configuration forimaging said scene at an exposure plane; reflecting means movablebetween a viewing position and an exposure position for selectivelyconverting said optical path from one said configuration to the other;erecting linkage means coupled with said reflecting means and actuableto move said reflecting means between said viewing and said exposurepositions; drive spring means for providing a rotational output ofpredetermined characteristic; actuator means drivably engageable withsaid linkage means and responsive to said drive spring means output foractuating said erecting linkage means to move said reflecting means froma select one of said positions to the other; motor means having anoutput connected in driving relationship with said actuator means forcausing said actuating means to actuate said erecting linkage means tomove said reflecting means into said one of said positions; andovertravel means coupled between said actuator means and said erectinglinkage means and operative as a lost-motion connection with said motormeans when said reflecting means is restrained.
 3. The reflexphotographic apparatus of claim 2 in which said drive spring means is alow-rate multi-turn torsion drive spring having a predetermined residualtorque when said reflecting means is in said other position.
 4. Thereflex photographic apparatus of claim 2 in which said overtravel meansis a low-rate multi-turn torsion spring positioned concentrically withsaid drive spring means.
 5. The reflex photographic apparatus of claim 2in which: said drive spring means is a multi-turn torsion drive springhaving a predetermined residual torque when said reflecting means is insaid other position; said actuator means includes sleeve means fordrivably engaging said erecting linkage means; and said overtravel meansis positioned coaxially with said sleeve means and said drive spring. 6.The reflex photographic apparatus of claim 5 in which said overtravelmeans is operative to effect said engagement between said sleeve meansand said erecting linkage means.
 7. The reflex photographic apparatus ofclaim 6 in which said overtravel means is present as a multi-turntorsion spring.
 8. The reflex photographic apparatus of claim 6 in whichsaid sleeve means is drivably engageable with said drive spring.
 9. Thereflex photographic apparatus of claim 8 in which said motor means isoperative, when energized, to rotate said sleeve means so as to loadsaid drive spring.
 10. The reflex photographic apparatus of claim 9 inwhich said sleeve means is configured to rotate out of said engagementwith said erecting linkage means when said reflecting means isrestrained and said motor means is energized.
 11. The reflexphotographic apparatus of claim 6 in which said erecting linkage meansis present as a four-bar linkage.